Twinning by exchange of two statical units 5

a) 1.Sxc5+!
1...Kd5 2.Rxe5+
1...Kxe3 2.Qxd3+
1...Kf5 2.Qxf3+

b) 1.Sxg5+!
1...Kd5 2.Qxd3+
1...Kxe3 2.Qxf3+
1...Kf5 2.Rxe5+

The role of twinned units is clear - the line of bishop action determines the key and both king and bishop do their guarding job. This Lacny cycle suffered in Stefan Sovik's jubilee tourney from duals in mating moves in b) position.

a) 1.Qe6! th. 2.Sd7#
1...Ke3 2.Sg4#
1...Kxc3 2.Sxc4#
1...Kc5 2.Sxd3#

b) 1.Qf5! th. 2.Sg4#
1...Ke3 2.Sxc4#
1...Kxc3 2.Sxd3#
1...Kc5 2.Sd7#

Position of twinned bR determines once again the key as wQ must in key prevent its unguard. Moreover rook precises some variations, and both rook and pawn block potential. It can be said they are very well used in this 4-fold Shedey cycle. One can note that rook has (weak) defence possible, in a) e.g. 1...Rc5, but I'd admit such a problem into competition as this variation is clearly unthematical.

a)
1.Rc3! th. 2.Bf7+
1...dxe4 2.Re3 d5 3.c5 a2#
1...dxc4 2.d5+ Ke5 3.Rxc4 a2#

1.Re3! zz
1...dxe4 2.d5+ Ke5 3.Bb6 a2#
1...dxc4 2.Rc3 d5 3.e5 a2#

b)
1.Rc3? th. 2.Bf7+, 1...dxc4!

1.Re3? zz, 1...dxe4!

1.Rf3! zz
1...dxe4 2.Re3 d5 3.c5 a2#
1...dxc4 2.Rc3 d5 3.e5 a2#

Very special case. Cyclone theme - Kiss cycle - is executed fully in a) position, while in b) position we can see Vladimirov theme (or rather pseudo-Vladimirov, as both solution continuations are prepared already in a set play).

a) 1.cxb6! th. 2.Sxd6#
1...Kd5 2.Sf3#

b) 1.Sxd6! th. 2.Sf3#
1...Kd5 2.cxb6#

Djurasevic cycle, 4th basic horizontal cycle requiring only 2 phases. Both twinned knight and pawn play important roles in new-strategical mechanism as well as in keeping the problem sound, royal defence causes unpin of bS in a) and unguard of half-battery line in b). Very well done.